Introduction

Coccidioidomycosis, often referred to as “Valley Fever,” is an uncommon but extremely severe disease in cats, dogs and people that develops after inhalation (or less commonly, ingestion) of infectious microorganisms released by spores of the fungus, Coccidioides immitis. This fungus naturally occurs in soil and thrives in the hot, dry areas of the southwestern United States, Mexico and parts of Central and South America. Cats are particularly resistant to developing clinical disease as a result of infection by this microorganism; most cats exposed to the fungal spores never show signs of illness and develop immunity to the organism. Unfortunately, some cats will develop clinical disease, which can rapidly become life-threatening. When symptoms do develop in cats, they almost always include weeping skin lesions.

Treating Valley Fever in Cats

The therapeutic goals for this disease are preventing further dissemination of the microorganisms, eradicating the fungal organisms and improving or at least maintaining the patient’s quality of life. Most cats are treated as outpatients. Supportive care for these cats involves restricted activity until clinical signs of infection resolve. They should be fed a high quality, palatable diet with free access to fresh water at all times. If necessary, oxygen supplementation can be provided on an inpatient basis.

Diagnosis should be rapidly followed by oral anti-fungal therapy. The anti-fungal drugs currently available for feline treatment include itraconazole, ketoconazole and fluconazole, although of course with time newer medications may become available. Ketoconazole can be effective and is the least costly, but it carries more adverse side effects than the other two anti-fungals, including liver damage, vomiting and inappetance. Itraconazole is more expensive than ketoconazole and may or may not have fewer side effects. Fluconazole has the best penetration of the eye and central nervous system but is the most costly. Whichever anti-fungal medication is chosen by the attending veterinarian, it must be administered precisely in accordance with the veterinarian’s instructions. This will normally be twice daily, for at least one year. Long-term use of azole drugs can cause liver dysfunction, gastrointestinal upset and adverse skin reactions, so treatment must be closely and regularly monitored.

Unfortunately, clinical disease in cats typically involves systemic infection. The prognosis is guarded to grave.